Physics and Surveys

So there’s this concept in physics which states that the very act of observing something has an effect on that thing. For example, to see a molecule, we need to hit it with electrons, and those electrons cause a change in that molecule. The same can be said of larger things. If you go to Africa to observe a pride of lions, the very act of observing them causes them to behave in a different manner than they would if you were not there.

The same concept applies to surveys.

We had a discussion today where one of my fellow students told us that she was taking a class in survey design. One of her assignments was to go to a market in Baltimore and survey people on their daily activity habits. She said she felt guilty because some of the people who answered her survey told her that they hoped something good would come of her “study.” Except it wasn’t a “study,” per se. It was an assignment for her class.

I’m not going to get into the ethical discussion about this thing because we’d need to make drawings on the back of napkins and use straws to construct models and diagrams. It would take a long time. I just wanted to point out to you aspiring epidemiologists out there that the very act of observing a population (and taking measurements from it) changes that population.

For example, if you do a simple survey asking people how many steps they think that they take a day, there are going to be some respondents who will try to walk more because they are reminded that they don’t walk enough. Also, if the surveyor makes a face or says something in response to the answer (e.g. “1,000 steps? Oh, boy.”), that is going to have an effect on the person being interviewed. It happens all the time, even in larger studies.

There are many documented cases where large, randomized, double-blind, placebo-controlled trials are ruined because of the interaction between researcher and subject. If the study subjects know that this is a study on a blood glucose medication, they may be more likely to eat sugary foods because they think that the new medication will keep them safe or they may be less likely to eat sugary foods on the 50/50 chance that they are in the placebo group. These are all things that we need to think about.

It also applies outside the world of public health and research. You saw how asking about “Obamacare” versus “Affordable Care Act” changed people’s opinions about it. How you ask the question, how you — the researcher — react to the answer, and what you’re asking makes all the difference. Be aware of that if and when you do research and when you read research… Ask yourself how the uncertainty principle applied to the results you’re seeing.